This invention relates to an air intake for a large internal combustion engine on a large truck. The engine may either be a diesel or a gasoline engine.
To protect such expensive engines from damage by ingestion of road dust, the air inlet system conventionally includes an air cleaner. Ambient air is supplied to the air cleaner through an inlet or snorkel pipe, usually in the form of a large riser extending vertically upwardly behind the truck cab.
The elimination of moisture from such air intake systems has typically been provided for by a moisture-eliminating cap or hood at the top of the snorkel pipe, or by filters or other restrictions in the pipe itself. In addition to preventing the direct falling of precipitation into the vertical pipe, the caps have also been provided with internal devices that collect and eject moisture which enters the cap due to the forward motion of the vehicle. Examples of such intake caps are disclosed in U.S. Pat. Nos. 3,987,862 and 3,791,112 where cross sectional narrowings, configuration changes, and tangentially directed vanes have been used for centrifugal separation of the moisture from the air; thereafter the collected water passes out through a drain opening in the cap. These moisture removal systems, however, all restrict the flow of air through the system, and in large engines all such restrictions unduly limit the supply of air to the engine.
In order to get the maximum amount of air to flow to the intake, ram air systems have been designed to scoop the air from the direction of travel and feed it to the engine, thereby taking advantage of additional air pressure. Reducing the water intake by rotating the cap so that the air intake faces the direction opposite the vehicle's movement is undesirable because it interferes with the ram air effect, resulting in reduction of air intake when the truck is moving at high speed.
Attempts to eliminate moisture at or near the air cleaner have heretofore been unsatisfactory also. Some such systems provided for a discharging check valve at the bottom of the air cleaner, but disclosed a check valve which opened to permit drainage only when the engine was shut off, the valve being held closed by the negative pressure of the air intake during engine operation. This system made possible the accumulation of large amounts of water inside the air cleaner during rainstorms. Moreover, it is preferred to remove the water upstream from the air cleaner in order to prevent rusting it or wetting the filter element and thereby hampering its cleaning action.
Thus, heretofore the elimination of moisture from the air inlet systems of large trucks and the like has remained a problem. It has been difficult to take advantage of the ram air characteristics of a forward facing air cap, without restricting the forced air flow.
It is therefore, an object of the invention to provide an air intake system which separates moisture from the air without interfering with the maximum flow of air to the truck's internal combustion engine.
Another object of the invention is to provide a low-restriction air intake system which has a large air flow capacity, yet which occupies a minimum of space between the back of the tractor cab and the trailor in large trucks and the like.
Yet another object of the invention is to provide a low-restriction air intake system which substantially eliminates moisture from the air before it passes to the air cleaner.